Fusing mechanism for a xerographic copying machine



Sept. 16, 1958 H. E. CRUMRINE ETAL 2,852,651

FUSING MECHANISM FOR A XEROGRAPHIC COPYING MACHINE Filed Nov. 2, 1953 4 Sheets-Sheet 1 FIG. I

INVENTORS HERBERT E. CRUMRINE WILLIAM G. LEWIS LYDE R. MAYO ATTORNEY Z SSZ SSE Sept 31%, EQS H. E. CRUMRINE ETAL FUSING MECHANISM FOR A XEROGRAPHIC COPYING MACHINE 4 Sheets-Sheet 2 Filed Nov. 2 1953 u Imq AT TORN EY Sept. 16, 1958 FIG. 3

FUSING MECHANISM FOR A XEROGRAPHIC COPYING MACHINE Filed Nov. 2 1953 4 Sheets-Sheet 5 INVENTORS HERBERT E. CRUMRINE WILLIAM G. LEWIS CLYDE R. MAYO Patented Sept. 16, 1958 FUSING MECHANISM FOR A XEROGRAPHIC COPYING MACHINE Herbert E. Crumrine, William G. Lewis, and Clyde R. Mayo, Rochester, N. Y., assignors to Haioid Xerox Inc., a corporation of New York Application November 2, 1953, Serial No. 389,549

3 Claims. (Cl. 219-19) This invention relates to fusing mechanism for a xerographic copying machine of the general type including a rotating drum having an insulating image surface thereon and acting in cooperation with charging and powder-developing devices arranged around the drum, together with, feeding means for moving a transfer sheet past and in contact with a portion of the drum and image-transfer means to effect transfer of the powder image from the drum to the transfer sheet, after which the powder image is afiixed to the transfer sheet by fusing mechanism, and it has for its purpose to afford means for quickly achieving maximum fusing temperature so that sufficient heat is available almost immediately upon starting the ma- :hine, while protecting the transfer sheet against excessive heat by holding the temperature after the initial maximum heat has been attained, and also guarding the sheet when the machine is not in operation and the transfer sheet is stationary by means of devices associated with the fusing mechanism which function automatically to bar .he heat of the fusing mechanism from the transfer sheet and thus prevent burning of the transfer sheet.

More particularly the invention has for its object to provide means for controlling the voltage to the heating :oils so that increased voltage is sent through the heating :oils immediately on starting the machine and the voltage reduced after maximum heat is achieved, in conjunction with a shutter r shutters movable to a position between :he transfer sheet and the fusing mechanism and governed intomatically by the fusing mechanism so that when the after is in operation, the shutters move automatically way from the position between the transfer sheet and fusing mechanism, and when the fusing mechanism is out Jf operation and the machine shut down, the fusing nechanism functions automatically to project the shutters nto position between the fusing mechanism and paper and )IOtCCl', the latter against fire.

A further purpose of the invention is to provide simple, )ractical, and efficient electrically controlled devices gov- :rned by the fusing mechanism and including a springvensioned solenoid or equivalent unit which acts when vurned in one direction to move the shutters to their affective or closed position between the fusing mechanism ind transfer sheet, and whenvturned in the opposite di- 'ection to move the shutters away from such position and :xpose the traveling paper sheet with the powder image hereon to the action of the fusing mechanism.

To these and other ends, the invention consists in the :onstruction and arrangement of parts that will appear :learly from the following description when read in conunction with the accompanying drawing, the novel feaures being pointed out in the claims following the speciication.

In the drawings: a

Fig. 1 is a diagrammatic side elevation of a xerographic continuous copying machine for reproducing mi- :rofilm or the like and showing the application thereto of l preferred embodiment of the invention;

Fig. 2 is a vertical sectional view taken centrally of the fusing mechanism;

Fig. 3 is a bottom plan view of the same;

Fig. 4 is a transverse vertical sectional view taken on line 4-4 of Fig. 2;

Fig. 5 is a view in end elevation looking from right to left of Fig. 2, and i Fig. 6 is a diagrammatic view of the circuit controlling voltage to the heating coils.

The invention is illustrated in connection with a xerographic machine such as employed for copying images from microfilm, although applicable to any xerographic copying machine in which a sheet of paper or other transfer material is moved in contact with a portion of a rotating drum to permit transferring a powder image from the drum to the paper, and referring more particularly to the drawings in which like reference numerals refer to the same parts throughout the several views, 1 designates the drum provided with the usual insulating surface which may or may not be photo-conductive depending on whether the machine is employed for reproducing from exposed film or reproducing from master images carried on the drum, which is rotated by suitable drive mechanism, while 2 designates the microfilm to be copied in the disclosed embodiment, and which is moved from a supply roll 3 onto a receiving roll 4 by suitable mechanism. 5 designates a lamp housing for projecting images from the microfilm 2 through a lens system, light barrel 6, and slit 7 onto the drum. I

The surface of the xerographic drum 1 as it rotates is first operated on by brushes 8 which remove any powder adhering from a previous operation, then subjected to the action of a discharge lamp 9 which dissipates any electro static charges remaining on the drum or created by the cleaning brushes 8, after which a charging grid 11 operates to charge electrostatically the photo-conductive or other insulating surface of the drum immediately before it passes under the slit 7 through which the image is projected, resulting in the formation of a corresponding elec trostatic image on the drum.

Following this, the exposed surface of the drum passes under an electrometer 12 to give an indication of the amount of charge on the drum and thence through a developer chamber 13 in which a developer mixture of carrier and toner particles is cascaded over the charged surface of the drum, the toner particles adhering to the electrostatic image to form a powder image.

After leaving the developer chamber, the charged and image-bearing area of the drum preferably passes over a regenerating grid and lamp, following which the drum moves into contact with a continuously traveling web of paper or other transfer material indicated at 14, which is fed from a supply roll 15 and travels initially from the supply roll in between drag rolls 16 and 17 and thence around upper drag roll 16 into contact with the imagecarrying surface of the drum 1. The paper or other transfer sheet is held against the drum by the upper drag roll 16 and guide roll 18 over which the paper travels after leaving the drag rolls and drum 1. The paper web after leaving guide roll 18 travels in a horizontal plane through a fire-snufiing chamber 19 and under fusing mechanism which will be described more fully hereinafter and which includes a fusing unit 21, and thence between upper and lower drive rolls 22 and 23 which grip the paper with sufficient tension to draw it through the machine from drag rolls 16 and 17 around the image-carrying portion of the drum and over the guide roll 18.

After leaving drive rolls 22 and 23, the paper web travels to a receiving roll 24 onto which it is wound and from which the completed roll of paper may be removed after the-powder images have been permanently affixed by the fusing unit 21. The receiving roll24, drive rolls 22 and 23, guide roll 18, and drag rolls 16 and 17 are alloperated by suitable mechanism preferably as shown in copending application S'erialNo. 389,098} filedTO'ctober 29, 1953, Patent No. 2,781,705, and the details of'which form no part of the present invention. 25' designates a charging grid'located in spaced relation to the path of the paper where it contacts the drum 1, preferably intermediate the drag roll'16 and guide roll'i3, and operating to impose an electrostatic chargeonthe paper and thereby hold the paper against the drumand effect transfer of the powder images from the surface;of the drum. of thepaper at a point directly opposite the; portion of the paper sheet which is in closest contact with or tangential to the adjacent surface of the drum.

The fire-snufiingchamber 19 comprisesv a narrow enclosing chamber open at both ends and through which the paper travels in spaced. relation to the surrounding walls and acting to snuif'out a fire which may accidentally occur as a result of the fusing operation, and the firesnufiing chamber 19 may be provided with suitable mechanism not shown including a device in contact with the paper sheet and operating in conjunction with aswitch to stop operation of the machine if the web is broken by fire, and in conjunction with stopping of the machine or the paper feed, it is desirable to protect the paper web immediately from .the fusing unit.

After the paper passes from the fire-snufiing chamber 19, the powder image which is carried on the paper or transfer sheet is afi'lxedby the fusing unit .21.which operates to secure the powder imagepermanently to the paper by heating and softening the powder forming the image, and the present invention has to do more particularly with mechanism for bringing the fusing unit to maximum fusing temperature quickly upon starting the machine following which the temperature is maintained, and for protecting the paper against overheating or burning by placing a barrier between the fusing unit and the paper, in the event of variation of conditions or stoppage of the machine or paper feed.

In order to protect the paper against overheating or burning, there is provided a means preferably in the form of a shutter or pair of shutters that are automatically interposed between the fusing unit and .the transfer sheet whensthe operation of the fusing unit or feed of the paper is stoppedfor any reason, the shutters being withdrawn from suchposition when the fusingunit resumes operation, such automatic control being, governed by an electrical unit in the circuit which. controls the fusing unit 21 and thedetailed mechanism, forgoverning the shutters formingpart of the fusing mechanism will now be described.

Referring; to Fig. 4, 21 designates the heating elements forming the fusing-,unitj and preferably comprising coils of Nichromewire which are quickly heated to maximum temperature upon starting'the machine and retained at a temperature suflicient to fuse the developer particles onto the paper, while located immediately above and partially surrounding the resistance wires is a reflecting .shield including an outer stiff supporting plate of steel indicated at 27 and an inner plate 28 of aluminum, which acts to reflect and concentrate the heat, onto, thetransfer sheet to effect fusing of the-developer powder image.

29 designates apair of shutters which are movable from the full-line position shown in Fig. 4 to the position illustrated'in dotted lines in which they are located between the fusing unit and the transfer sheet so as to protect the latter against the during shut-down of the machine, the shutters being movable to such protecting position immediately upon opening the circuit to the fusing unit or resistance wires 21.

To accomplish this, the shutters 29 are mounted on vertically extending legs 31 each of which is pivoted at its upper end on a horizontally disposed supporting rod initial'images reaching the fuser, and immediately the.

32. Intermediate the upper and lower extremities of the legs 31 are connecting links 33 pivoted to the legs 31 at their outer ends and pivotally connected at their inner ends to opposite ends of arms 34 which are fixedly secured to a spindle 35 and extend in opposite directions from the spindle 35. Thus when the spindle 35 is turned in one direction, the connecting links 33 operate to move the legs; 31 inwardly to close shutters 2%, and when the spindle 35 is turnedin. theoppositedirection, the connectiinlrs 33 operate to move the shutters 29 to open position, as shown in full lines in Fig. 4-, at which time the paper is exposed to the heating effect of the fusing unit 21 Thespindle 35 is connected by a'suitable joint 36-with the arbor 37 of a rotary solenoid 33 which may be of conventional construction as well known in the art and interposed in the electrical circuit which governs the fusing unit 21, the solenoid arbor 37 being turned in one direction by closingof 'the fusing unit circuit to open shutters 29 and returned to its original position whenthe circuit is broken by. a spring, to restore the shutters to their closed or dotted-line position as illustrated in Fig. 4, such' a spring-tensioned rotary solenoid being well known in the art and requiring no detailed disclosure. The arbor 37 of the spring-tensioned solenoid may also be provided witha cam 39 for operating a microswitch 41 to cut ina suitable resistance element after the fusing unit circuit is closed and thus protect the solenoid against excessive current, as well known in the art.

it is essential in conjunction withsuch a fusing mechanism to carry off the fumes and excessive heat generated by fusing. the developer powder onto the transfer sheet, and to accomplish this there is provided an air chamber entirely surrounding the fusing mechanism and shutter mechanism on the top and sides, such chamber being indi' cated at 42 and formed by inner and outer walls .43 and 44 respectively, which extend at their lower ends to a point in proximity to the transfer sheet, see Fig. l. The inner and outer walls 43 and 44 terminate somewhat above the path of the transfer paper which travels in close proximity below the fusing unit and the open bottom of the surrounding chamber 42.

The outer Wall 44 is provided with an opening 46 at its top which communicates with a conductingpipe 47 that leads to a point outside the housing and which may contain a suitable exhaust fan 48 for drawingofftheheat and fumes of combustion from the chamber surrounding the fusing mechanism.

In order to heat the fusing unit quickly to maximum temperature when starting the machine, there is provided a voltage control unit 49 which is governed by an automatic timer 50 that operates in conjunction with relay 51 and transformer 52 to impose on the heating unit an initial high voltage of approximately 153 volts. After a predetermined period, timer 5t) deenergizes relay 51 and operates relay 53 to cut out transformer 52 and reduce the voltage tothe heating unit to approximately volts. Thus the heat is sufiicient to fuse the powder image as soon as the portion of the paper carrying the image reaches the fuser, and immediately thereafter the voltage is reducedvto prevent overheating and burning the paper transfer sheet. line.

The operation briefly is as follows: When the machine is first started, the fusing unit heats up rapidly to its operating temperature and the shutters 29 are moved to open position, so that full heat isavailable to fuse-the voltage to the fusing unit reduces so as to maintain the temperature at a safe point to prevent overheatingor burning the transfer sheet. The parts are then in normal operation for feeding the paper and fusing powder=images onto the paper, the shutters 29 being in open position as illustrated in full lines in Figs. 1 and 4, and held open by spindle 35 through the closing of the electrical circuit,

54 is a manual switch controllingthenot shown, to the rotary solenoid 38. When the machine is shut down and the circuit to the fusing unit 21 is opened for any reason, automatically or otherwise, the solenoid 38 is instantly deenergized and spindle 35 thereupon released and turned by a spring within the solenoid unit to the position shown in dotted lines in Fig. 4, and the shutters moved to closed position, affording a barrier or closure between the fusing unit 21 and the transfer sheet.

While the invention has been described with reference to the details and construction herein illustrated, it is not confined to the exact mechanism shown, and this applica tion is intended to cover such modifications or departures as may come within the purposes of the invention and the scope of the following claims.

We claim:

1. In a xerographic reproducing apparatus wherein fusible xerographic powder images are formed on a movable support surface and are fused thereon by means of an electrically energized heating unit that is arranged in spaced relation to the path of movement of the support surface, the combination of a rotatably mounted shutter mechanism movable to an effective position to shield the support surface from the heating unit and to an ineffective position to expose the support surface to the heating unit, a rotary solenoid operated in conjunction with the heating unit for moving the shutter mechanism to its ineffective position, and resilient means for moving the shutter mechanism to its effective position upon the cessation of operation of the actuating means. a

2. In a xerographic reproducing apparatus wherein fusible xerographic powder images are formed on a movable support surface and are fused thereon by means of an electrically energized heating unit that is arranged in spaced relation to the path of movement of the support surface, a combination of a rotatably mounted shutter mechanism movable to an effective position to shield the support surface from the heating unit and to an ineffective position to expose the support surface to the heating unit, actuating means for moving the shutter mechanism to its ineffective position, said actuating means including an oscillatory spindle operatively connected to the shutter 6 mechanism and a rotary solenoid operated in conjunction with the heating unit for actuating the spindle, and resilient means for moving the shutter mechanism to its effective position upon the cessation of operation of the actuating means.

3. In a xerographic reproducing apparatus wherein fusible xerographic powder images are formed on a movable support surface and are fused thereon by means of an electrically energized heating unit that is arranged in spaced relation to the path of movement of the support surface, the combination of a shutter mechanism movable to an effective position to shield the support surface from the heating unit and to an ineffective position to expose the support surface to the heating unit, said shutter mechanism including a pair of shutter elements operable to shield the support surface, vertically extending legs for supporting the shutter elements, a supporting rod on which said legs are pivotally mounted for laterally swinging movement, an oscillatory spindle having arms fixed thereon and extending in opposite directions from the spindle, links connecting the outer end of said arms With said legs, a rotary solenoid operated in conjunction With theheating unit for oscillating the spindle to move the shutter elements to their ineffective position, and resilient means for moving the shutter elements to their effective position upon the cessation of operation of the solenoid.

References Cited in the file of this patent UNITED STATES PATENTS 1,148,138 Barr et a1 July 27, 1915 1,439,091 Geyer et a1 Dec. 19, 1922 1,758,619 Phillips May 13, 1930 2,357,809 Carlson Sept. 12, 1944 2,472,293 Groven June 7, 1949 2,477,099 Thompson et al July 26, 1949 2,515,846 White et al. July 18, 1950 2,600,849 Collins et a1 June 17, 1952 2,624,652 Carlson Jan. 6, 1953 2,629,162 Peck Feb. 24, 1953 2,703,280 Butterfield et a1. Mar. 1, 1955 

